Rare or unusual HLA antibodies are essential to accurately type donors and patients for procedures such as bone marrow transplantation. These antibodies are only available from humans who have developed the antibodies in response to pregnancy or transfusion. The protocol is designed to permit restimulation of previously identified antibody by infusion of a small quantity of allogeneic lymphocytes. Donors of such lymphocytes are rigorously screened and are often the spouses of the subject. One subject has completed the protocol. A rare anti-A33 antibody was restimulated by infusion of lymphocytes from the spouse. Plasmapheresis of this subject permitted the harvesting of sufficient antibody to be useful for typing and sera exchange activities.